1. Field of the Invention
The invention relates to light emitting devices and more particularly to light emitting devices including at least one light-emitting diode and phosphor, the phosphor including copper and converting the wavelength of light which is generated from a light-emitting diode.
2. Description of the Related Art
Light emitting diodes (LEDs), which have been used for electronic devices, are recently used for automobiles and illumination products. Since light emitting devices have superior electrical and mechanical characteristics, demands for light emitting devices expected to be increased. In connection to this, interests in white LEDs are increasing as an alternative to fluorescent lamps and incandescent lamps.
In LED technology, solution for realization of white light is proposed variously. Normally, realization of white LED technology is to put the phosphor around the light-emitting diode, and mix a part of primary emission from the light emitting diode and the secondary emission, which is converted the wavelength by the phosphor. For example, WO 98/05078 and WO 98/12757, disclose white light emitting diodes comprising, a blue light emitting diode, which is capable of emitting a peak wavelength at 450-490 nm, and YAG group material, which absorbs light from the blue light emitting diode and emits yellowish light (mostly), which may have different wavelength from that of the absorbed light.
However, in such an usual white LED, color temperature range is narrow which is between about 6,000-8,000K, and CRI (Color Rendering Index) is low which is about 60 to 75 so that only cold bluish white light is provided. Therefore, it is hard to produce the white LEDs with desired color coordination or color temperature, and particularly, there is limit of realizing the light similar to visible sunlight.
Moreover, white LEDs which are using humidity-sensitive phosphors have unstable luminescent properties in water, vapor or polar solvent, and this unstableness may cause changes in the luminescent properties of white LED.
Generally, a light emitting device for general illumination comprises a plurality of packed white LEDs, manufactured in a separate process, a printed circuit board on which the white LEDs are mounted, a protecting circuit and/or AC/DC inverter connected to the white LEDs, the LEDs being connected to each other via a circuit pattern formed on the printed circuit board.
However, to manufacture a light emitting device for general illumination having the aforementioned structure according to the prior art, there is a problem in that the metal wiring process should be performed for a large number of elements one by one so that processing steps increase in number and are complicated. As the number of the process steps increases, a fraction defective also increases, thereby impeding mass production. Further, there may be a case where metal wiring becomes an open circuit due to a certain shock so that the operations of light emitting elements are stopped. Furthermore, there is a disadvantage in that spaces occupied due to serial array of respective package of light emitting elements are expanded so that the size of a light emitting device for general illumination considerably becomes large.